Preliminary investigations on non-linear fluid-structure interaction of an offshore structure

Abstract

Fluid-structure interaction (FSI) of offshore structures is an important area of research. It is also of significant industrial value, where such capabilities could be used for simulating the structural response in numerical wave tanks. The current research focuses on the development of a numerical wave tank with FSI capabilities. This requires solving the non-linear fluid and structure behaviour in the time domain considering a non-linear velocity potential formulation for the wave flow and a linear elastic formulation for the structure. The fluid and structural behaviour are coupled in time through a mixed Lagrangian-Eulerian procedure and the differential equations are discretized using the finite element method. Unstructured triangular meshes are used to discretize the fluid and structural domain, augmented by mesh smoothing algorithms. Based on the studie, it is shown that the transient force developed by the fluid on the structure varies due to the elastic nature of the structure. The perturbations in the free-surface profile due to the structural response are also captured. It is also shown that transient non-linear studies are important as they can help in identifying critical design limitations of traditional guides. It is thus demonstrated that the present work is capable of solving such FSI problems in order to obtain a reliable and complete analysis leading to a better understanding and safer design of compliant structures. The effect on the structure due to prolonged interaction with the fluid needs to be further studied for a better understanding.